1. Field of the Invention
This relates to a magnetic tape cassette, and more particularly to a structure of a magnetic tape cassette.
2. Description of the Prior Art
In a magnetic tape cassette, in general, as shown in FIGS. 10 through 12, a hub 1 around which a magnetic tape is wound and slidable sheets (not illustrated) disposed on upper and lower surfaces of said hub, respectively, are housed between upper and lower half members 3 and 5. Further, in the front portion of the magnetic tape cassette, guide rollers and tape guides 7 for guiding said magnetic tape are provided. In the rear portion of the magnetic tape cassette, holes 4 are provided with claws 2 for preventing erasure by mistake and holes 6 are provided for detecting the kind of a tape. The holes 6 for detecting the kind of a tape are different in their positions, shapes and dimensions according to the kind of a tape. Moreover, the rear surface portion of the magnetic tape cassette which includes holes 4 and 6 are monobloc-formed with the other portion which does not include the holes. Accordingly, on the occasion of injection molding of the above-described magnetic tape cassette, an exclusive mold for injection molding is necessary for each kind of tape. However, since such an exclusive mold for injection molding is expensive, waste in production cost and deterioration of efficiency are inevitable especially in the case of small production of many products. Further, since the holes 6 are formed at the same time of forming holes 4 in the upper and lower half members 3 and 5 of the above-described magnetic tape cassette, the surrounding walls of the holes 4 and 6 produce portions having complicated shapes and thick portions at the rear surface portion. This causes generation of shrink marks on the surface of the case. This is accompanied by rejects of cases relative to shape and accuracy, and often affects the functions and characteristics of cassettes.